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71.
We present a mean-field approach for calculating thermodynamic properties(free energies) of protein–solvent systems. We apply this method to thetumor suppressor protein p53, where we study the stability of itstetramerization domain when subjected to site-directed mutagenesis. Acomparison with experimental results is included. 相似文献
72.
Analytic models based on discrete-time Markov chains (DTMC) are proposed to assess the algorithmic performance of Software Transactional Memory (TM) systems. Base STM variants are compared: optimistic STM with inplace memory updates and write buffering and pessimistic STM. Starting from an absorbing DTMC, closed-form analytic expressions are developed, which are quickly solved iteratively to determine key parameters of the considered STM systems, like the mean number of transaction restarts and the mean transaction length. Since the models reflect complex transactional behavior in terms of read/write locking, data consistency checks and conflict management independent of implementation details, they highlight the algorithmic performance advantages of one system over the other, which – due to their at times small differences – are often blurred by implementation of STM systems and even difficult to discern with statistically significant discrete-event simulations. 相似文献
73.
74.
Christine Bratrich Bernhard Truffer Klaus Jorde Jochen Markard Werner Meier Armin Peter Matthias Schneider Bernhard Wehrli 《河流研究与利用》2004,20(7):865-882
Hydropower is the most important renewable electricity source worldwide. It shows clear advantages for the global CO2 balance but creates serious ecological impacts on a local scale. As a consequence, concern for the conservation of natural river ecosystems is growing within society and more people are willing to pay extra for so‐called ‘green electricity’. The definition of ‘green’, however, is not straightforward and customers cannot directly examine the quality of electricity products. Therefore, credible certification of high ecological standards is essential for successful green electricity marketing. In this paper we introduce a new assessment procedure for evaluating environmentally compatible hydropower production. This so‐called ‘Green Hydro’ concept was developed in the context of a multidisciplinary case study on a 400 MW hydropower scheme in the Southern Alps of Switzerland. The concept guarantees both general standards for different schemes operating in different types of watersheds and flexibility for local particularities. We developed an environmental management matrix that considers basic criteria and eco‐investments and covers five environmental areas of concern (i.e. hydrological character, connectivity, morphology, landscape, and biological communities). The ecological perspective is complemented by five management domains (i.e. instream flow regimes, hydropeaking, reservoir and bedload management, and power plant structures). Applying assessment and modelling tools for the Green Hydro procedure showed that dynamic habitat models allowed quantification of the effects of different instream flow regulations at morphologically distinct sites. In this case, morphological restoration could be more beneficial than increasing the minimum flow. The first experience with the Green Hydro certification is encouraging. So far, 13 facilities have successfully passed the certification procedure. They produce a total of 186 GWh green electricity per year, which is sufficient for the supply of almost 40 000 households in Switzerland. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
75.
Armin De Meijere Klaus Michelsen Rolf Gleiter Jens Spanget-Larsen 《Israel journal of chemistry》1989,29(2-3):153-164
The syntheses of the new hydrocarbons trimethylenetriasterane 12 , trispirocyclopropanetriasterane 3 , trispirocyclopropanenortricyclane 4 , and of the trispirocyclopropanenorbornanes 5, 6 , and 7 are reported. 12 contains six vinylcyclopropane units rigidly held in an antiperiplanar (ap) conformation in a D3h symmetric framework. 3 and 4 are the first model compounds with bicyclopropyl units rigidly fixed in an s-trans (ap) conformation (Θ = 180°). Their PE spectra reveal that the interaction parameter βww = −1.73 eV for this arrangement is the same as that for Θ = 0°. 相似文献
76.
77.
78.
In this work, commercially available white paint is applied as a pigmented diffuse reflector (PDR) on the rear surface of thin-film crystalline silicon (c-Si) solar cells with a silicon thickness in the 1–2 μm range. We show that white paint increases the short-circuit current density of the solar cells enormously, with a boost of 41% observed for very thin planar solar cells illuminated with the global AM1.5 solar spectrum. We also show that white paint is a better back surface reflector (BSR) than aluminium, air, a transparent conductive oxide (TCO)/aluminium stack, and even a detached aluminium mirror. While previous studies have investigated the influence of PDRs on silicon solar cells with thicknesses of over 27 μm, this work closes the gap that has existed for much thinner cells. 相似文献
79.
Marcus Schoßig Armin ZankelChristian Bierögel Peter PöltWolfgang Grellmann 《Composites Science and Technology》2011,71(3):257-265
The damage mechanisms of short glass fibre reinforced polypropylene (PP) and polybutene-1 (PB-1) materials were investigated. For this purpose, in situ tensile tests were conducted in the environmental scanning electron microscope (ESEM) while simultaneously recording the acoustic emission (AE). To be able to observe damage mechanisms directly during loading, notched specimens were used. This method allows the direct correlation of the recorded load - elongation data with observed damage mechanisms, as well as correlations with acoustic emission data. Hence, it is possible to describe the damage kinetics of short glass fibre composite.It was found that different bonding conditions of the two investigated materials result in different damage mechanisms as well as in different AE behaviour. For fibre reinforced PP with excellent bonding conditions of the fibres in the polymeric matrix, fibre fracture, slipping of fibres in the delamination area, debonding and pull-out with matrix yielding was observed. The determined AE parameter amplitude Ap and energy EAE for the PB-1 material are lower because of the weak bonding of the fibres to the PB-1-matrix. Hence, energy dissipative damage mechanisms like pull-out with matrix yielding can occur only in a limited part of such materials. 相似文献
80.
Synthesis of novel tricalcium phosphate-bioactive glass composite and functionalization with rhBMP-2
Schickle K Zurlinden K Bergmann C Lindner M Kirsten A Laub M Telle R Jennissen H Fischer H 《Journal of materials science. Materials in medicine》2011,22(4):763-771
A functionalization is required for calcium phosphate-based bone substitute materials to achieve an entire bone remodeling.
In this study it was hypothesized that a tailored composite of tricalcium phosphate and a bioactive glass can be loaded sufficiently
with rhBMP-2 for functionalization. A composite of 40 wt% tricalcium phosphate and 60 wt% bioactive glass resulted in two
crystalline phases, wollastonite and rhenanite after sintering. SEM analysis of the composite’s surface revealed a spongious
bone-like morphology after treatment with different acids. RhBMP-2 was immobilized non-covalently by treating with chrome
sulfuric acid (CSA) and 3-aminopropyltriethoxysilane (APS) and covalently by treating with CSA/APS, and additionally with
1,1′-carbonyldiimidazole. It was proved that samples containing non-covalently immobilized rhBMP-2 on the surface exhibit
significant biological activity in contrast to the samples with covalently bound protein on the surface. We conclude that
a tailored composite of tricalcium phosphate and bioactive glass can be loaded sufficiently with BMP-2. 相似文献